Apparatus of the kind referred to above is disclosed in U.S. Pat. No. 4,317,314 and does not include means for laterally inclining the tool. Also, the apparatus is dependent on external forces for its propulsion usually by the operator pushing or pulling the apparatus in the desired direction, which especially in the case of large cutting depths requires considerable effort and so constitutes a major ergonomic inconvenience.
In similar apparatus in other areas, for example, sweeping machines of the type disclosed in U.S. Pat. No. 2,978,719, it is known that by angling the two brush shafts in a vertical plane at right angles to the direction of motion of the apparatus, and consequently also the brushes in relation to the floor, a certain driving force in a forward or rearward direction can be obtained.
The disadvantage of this latter solution is that the angling device is comparatively complicated and sensitive to damage and is scarcely suitable for heavier machines like grinders or millers where high contact pressure on the floor is required. Above all, the angling device becomes complicated when applied to grinding machines of the kind described in the above-mentioned Swedish patent with facilities for varying the contact pressure of the grinding or milling tool against the floor.